Since the transverse electric field is applied in the plane of metal atoms, its effect is added to the diagonal elements of the Hamiltonian matrix as a potential term. The mentioned term is calculated by multiplying the strength of the field to the y-coordinate of each atom while the lower (upper) edge of the nanoribbon is considered as the reference line. In addition, the bias voltage between leads changes the Fermi distribution function at left (right) lead equal to \(\mathit {f}(E+V_{DS}/2) (\mathit {f}(E-V_{DS}/2))\)  where \(V_{DS}\)  is bias voltage. The difference between these two distributions i.e., \([\mathit {f}(E+V_{DS}/2)-\mathit {f}(E-V_{DS}/2)]\)  should be considered in calculating the transmission probability [1]}. It should be noted, both the bias voltage and shedding light, place the system in the non-equilibrium condition. Thus, the self-consistent method should be used for calculating the transmission probability and spin polarization [1]}. It is important to note that we used the optimal values for energy of photons, intensity of light, and the intensity of \(E_{T}.y\)  which are 0.12 eV, \(20 nW/\mu m^{2}\) , and 0.2 eV, respectively in our mentioned numerical calculations. In other words, we found that, by altering the mentioned parameters, the spin polarization could be changed. Therefore, first, we calculated the optimum values for them aimed at getting the maximum spin polarization, and then the optimal values were exploited in our calculations.
